1. Field of the Invention
The present invention relates to an endoscope, or more particularly, to an endoscope having two bending portions of a first bending portion and a second bending portion.
2. Description of the Related Art
Endoscopes have an elongated insertion member thereof inserted into the stomach, the intestine or any other organ of a living body or a tortuous hollow of a machine. The stomach, the intestine, and other organs are three-dimensional and complexly tortuous. The insertion member of an endoscope must therefore be angled three-dimensionally finely.
For example, an endoscope described in Japanese Examined Patent Application Publication No. 5-16857 has an elongated insertion member composed of a first bending portion that is a distal portion and a second bending portion that is located at the proximal end of the first bending portion. Each of the bending portions has a plurality of joint pieces concatenated so that the pieces can rotate relatively to one another. Moreover, a sole angling mechanism is included in a control section of a hand-held unit included in an endoscope. The angling mechanism enables selective bending of the first and second bending portions.
The endoscope described in the Japanese Examined Patent Application Publication No. 5-16857 enables a user to selectively freely bend the first bending portion and second bending portion. However, since the sole angling mechanism is used to selectively bend the first and second bending portions, there is a fear that the bending portion different from the bending portion that must be bent may be manipulated incorrectly.
Moreover, the endoscope described in the Japanese Examined Patent Application Publication No. 5-16857 has a drawback that the two bending portions cannot be manipulated simultaneously.
Furthermore, when one of the bending portions of the endoscope described in the Japanese Examined Patent Application Publication No. 5-16857 is unused, the maneuverability of the endoscope is poorer than that of an ordinary endoscope having one bending portion.
The peripheries of the bending portions are sheathed with a bending rubber in order to keep the bending portions watertight. An amount of force required to bend the bending portions depends on the hardness of built-in components or the hardness of the bending rubber.
In order to bend the bending portions so that the bending portions will assume sufficient bending angles, it is necessary to apply a larger amount of force to the second bending portion than to the first bending portion. However, when a large amount of force is applied, a coil pipe may contract, the bending pieces may deform, or any other phenomenon may occur. While the use period of the endoscope gets longer, there arises a fear that the bending portions may not be able to bend to assume desired bending angles.
In order to overcome the poorness in bending smoothness, the ratio of built-in components to the inner diameter of the bending portion should be reduced by increasing the inner diameter. However, if the inner diameter of the bending portion is increased, the outer diameter thereof increases. This results in the poor inserting smoothness of the insertion member.